This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be easily implemented today, and the microphone is made of electret or ceramic.
This inverter amplifier is suggested by a technical documentation from Texas Instruments. The RF...
This circuit was obtained in old documentation, but it is valid for modern triacs that must be...
Found in English documentation, this timer produces an audio signal at the end of the timing. The...